1. Field of the Invention
The present general inventive concept is directed to an apparatus and method for controlling steam flow to heat supply water to provide tepid water at varying flow rates and to automatically and dynamically regulate the flow rates of steam and water to produce desired flow rates of tepid water within desired temperature limits. The inventive concept is useful in combination safety shower systems and other applications where rapid feedback control of fluid temperature is utilized.
2. Description of the Related Art
Numerous solutions have been devised and patented for the tepid water safety shower. Many improvements have also been directed to the purging of water from such systems to avoid bacteria and other concerns. Some inventions have used natural gas burners to create heat within the system. For instance, U.S. Pat. No. 8,209,796 discloses a safety shower that prevents stagnant water from causing a thermostat valve to open. This apparatus utilizes a gas burner to heat water in a hot water tank. U.S. Pat. No. 4,909,435 discloses a temperature controlled hot water delivery system that is controlled by valves and circuits. Other systems such as U.S. Pat. No. 6,270,014 also rely on microprocessors and electricity to control fluid systems. What is needed is a system that does not require an external power source, such as electricity, and can generate fluid at the desired temperature from a steam supply. U.S. Pat. No. 6,623,990 to Pirkle discloses a system that produces temperature-controlled water, however, the temperature control limits and response time of that system are not sufficient to achieve compliance with new industry standards. ANSI/ISEA standard Z358.1 was revised in 2009. This standard, entitled American National Standard for Emergency Eyewash and Shower Equipment includes many requirements including that the output water be between sixty degrees and one hundred degrees Fahrenheit and that the flow rate for a safety shower must be at least twenty gallons per minute. Additionally, the American Society of Sanitary Engineering Standard Number 1071 is entitled “Performance Requirements for Temperature Actuated Mixing Valves for Plumbed Emergency Equipment.” This standard requires that outlet water temperature should be between 65 and 95 degrees F. and shall not exceed 100 degrees F. under normal operation; that upon failure of the hot water supply, the cold water shall continue to flow; and cross flow or leakage shall not exceed 50 cc per minute.
The '990 patent disclosed a system whereby a downstream temperature sensor would activate at an overtemperature condition to send cold water back to the steam line to prevent the overtemperature condition. However, this operation requires time to operate and results in unsteady output temperatures. Once water fouls the operation of the heat controller, it again takes time to achieve desired temperature outputs. This and other temperature control systems provide temperature feedback that is too late to prevent overtemperature conditions, but instead reacts to overtemperature conditions.
What is needed is an automated water temperature control system that can generate desired temperature fluid with rapid response time, narrow temperature control, and safety features to ensure that over-temperature fluid is not delivered to a user. Further, what is needed is a system that does not require electricity, is self regulating, and requires only water and steam to operate.